ELEVATED LEVELS OF CYSTEINE PROTEASE ACTIVITY IN SALIVA AND SALIVARY-GLANDS OF THE NONOBESE DIABETIC (NOD) MOUSE MODEL FOR SJOGREN SYNDROME

Nonobese diabetic (NOD) mice develop an anti-exocrine gland pathology similar to human Sjogren syndrome, Recently, we demonstrated that NOD- scid mice develop severe loss of submandibular acinar cells with conco mitant appearance of abnormal isoforms of salivary proteins suggesting de novo enzymatic cleavage, Because these changes may indicate activa tion of apoptotic proteases, we examined saliva and salivary tissue fo r cysteine protease activity, Cysteine protease activities were elevat ed in saliva and gland lysates from 20-week-old NOD and NOD-scid mice as compared with age- and sex-matched BALB/c or 8-week-old NOD mice, T his activity appeared in the submandibular glands, but not in the paro tid glands, Western blot analyses using antibodies directed against sp ecific apoptotic proteases (interleukin 1 beta converting enzyme, Nedd -2, and Apopain/CPP 32) confirmed these findings, Submandibular glands from NOD-scid mice exhibited the greatest increase in proteolytic act ivity, indicating that infiltrating leukocytes are not responsible for these changes, Western blot analyses also failed to reveal changes in the levels of cystatins (saliva proteins that inhibit protease activi ty), Thus, increased cysteine protease activity appears to be directly related to submandibular acinar cell loss in NOD-scid mice involving the apoptotic pathway, Additional protease activity in saliva and glan d lysates of older NOD and NOD-scid mice, apparently mutually distinct from cysteine proteases, generated an enzymatically cleaved parotid s ecretory protein, We suggest, therefore, that proteolytic enzyme activ ity contributes to loss of exocrine gland tolerance by generating abno rmally processed protein constituents.